With the help of a 2004 NASA/JPL radar survey (left), an international team of archaeologists has created an expanded archaeological map of greater Angkor, revealing many previously undiscovered features. They found Angkor to be the most extensive urban complex of the preindustrial world.

The 2004 radar survey expanded upon one done in 2000. In both surveys, the NASA/JPL-developed Topographic Synthetic Aperture Radar/Airborne Synthetic Aperture Radar (Topsar/Airsar) imaging system scanned the area from aboard a NASA DC-8 aircraft.